Not Applicable
Not Applicable
The field of invention is electrical circuit interrupters, and more particularly to a dry high voltage circuit interrupter having an increased strike distance.
High voltage circuit interrupters are used to selectively interrupt the flow of electrical current through a circuit. As used herein, the term xe2x80x9chigh voltagexe2x80x9d means a voltage greater than 1,000 volts. Two types of high voltage circuit are generally in use, dry high voltage circuit interrupter and wet high voltage circuit interrupters. The primary difference between the two high voltage circuit interrupters is that the wet type is filled with oil, or some other dielectric fluid, which can leak.
Dry high voltage circuit interrupters typically include a vacuum interrupter encapsulated in an epoxy housing mounted to a frame. The vacuum interrupter includes a pair of electrodes, one being stationary and the other movable between an open position and a closed position to open and close the circuit. The movable electrode is typically mounted on the end of an operating rod which moves the moveable electrode between the open and closed positions.
The operating rod typically extends from the vacuum interrupter to engage an actuating mechanism mounted in the frame. The operating rod is insulated from the electrode to prevent the operating rod from conducting high voltage electrically energy from the electrode to the frame.
The housing typically includes an internal cavity for supporting the vacuum interrupter and operating rod. The shape of the internal cavity must also be designed to prevent high voltage energy from bridging the gap between the vacuum interrupter and the frame. The high voltage energy can bridge the gap by xe2x80x9ctrackingxe2x80x9d along the internal wall of the cavity formed in the housing, or by striking the frame directly through the cavity.
Tracking is a phenomena resulting from contamination or condensation forming on the internal cavity walls which allows electrical charges to creep along the surface of the internal cavity wall from a high potential at the vacuum interrupter to the frame which is at ground potential. Tracking can be minimized by increasing the distance the electrical charge must creep before reaching the frame. Typically, increasing the distance between the vacuum interrupter and the frame requires increasing the overall height of the circuit interrupter to increase the distance between the vacuum interrupter and the frame. Unfortunately, a larger, that is taller, circuit interrupter is not always desirable.
In one known dry high voltage circuit interrupter disclosed in U.S. Pat. No. 5,747,765, a vacuum interrupter is disposed in an upper end of an internal cavity formed in the housing. The housing is mounted to a frame, and the internal cavity is open to the frame. Convolutions formed in the internal wall of the cavity increases the length of the internal wall between the vacuum interrupter and the frame to minimize tracking.
Providing convolutions minimizes the problems associated with tracking and allows a shorter circuit interrupter. Unfortunately, the shorter circuit interrupter increases the chance for a direct strike between the vacuum interrupter and the frame because of the shorter physical distance between the two components. Accordingly, a need exists to minimize direct strikes between the vacuum interrupter and the frame.
The present invention provides a circuit interrupter including a housing having an internal cavity. The internal cavity includes a space at a first end thereof, and includes an internal wall extending from the space to a second end of the housing. A vacuum interrupter is disposed in the space. The vacuum interrupter has at least one movable contact for contacting at least one stationary contact. An operating rod extends through the cavity, and is operable to move the moveable contact At least one baffle is fixed to the operating rod, and disposed in the cavity. In a preferred embodiment, at least one step is formed in the wall. The step separates a first internal wall section from a second internal wall section, and the first internal wall section is closer to the space than the second internal wall section.
A general objective of the present invention is to increase the through-air strike distance between the vacuum interrupter and frame without increasing the overall height of the circuit interrupter. This objective is accomplished by providing a baffle in the cavity formed in the housing which blocks the most direct through-air path inside the housing between the vacuum interrupter and the frame.
The foregoing and other objectives and advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown by way of illustration a preferred embodiment of the invention.